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node_modules/eslint/lib/rules/dot-notation.js

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+/**
+ * @fileoverview Rule to warn about using dot notation instead of square bracket notation when possible.
+ * @author Josh Perez
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+const keywords = require("./utils/keywords");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+const validIdentifier = /^[a-zA-Z_$][a-zA-Z0-9_$]*$/u;
+
+// `null` literal must be handled separately.
+const literalTypesToCheck = new Set(["string", "boolean"]);
+
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "enforce dot notation whenever possible",
+            category: "Best Practices",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/dot-notation"
+        },
+
+        schema: [
+            {
+                type: "object",
+                properties: {
+                    allowKeywords: {
+                        type: "boolean",
+                        default: true
+                    },
+                    allowPattern: {
+                        type: "string",
+                        default: ""
+                    }
+                },
+                additionalProperties: false
+            }
+        ],
+
+        fixable: "code",
+
+        messages: {
+            useDot: "[{{key}}] is better written in dot notation.",
+            useBrackets: ".{{key}} is a syntax error."
+        }
+    },
+
+    create(context) {
+        const options = context.options[0] || {};
+        const allowKeywords = options.allowKeywords === void 0 || options.allowKeywords;
+        const sourceCode = context.getSourceCode();
+
+        let allowPattern;
+
+        if (options.allowPattern) {
+            allowPattern = new RegExp(options.allowPattern, "u");
+        }
+
+        /**
+         * Check if the property is valid dot notation
+         * @param {ASTNode} node The dot notation node
+         * @param {string} value Value which is to be checked
+         * @returns {void}
+         */
+        function checkComputedProperty(node, value) {
+            if (
+                validIdentifier.test(value) &&
+                (allowKeywords || keywords.indexOf(String(value)) === -1) &&
+                !(allowPattern && allowPattern.test(value))
+            ) {
+                const formattedValue = node.property.type === "Literal" ? JSON.stringify(value) : `\`${value}\``;
+
+                context.report({
+                    node: node.property,
+                    messageId: "useDot",
+                    data: {
+                        key: formattedValue
+                    },
+                    fix(fixer) {
+                        const leftBracket = sourceCode.getTokenAfter(node.object, astUtils.isOpeningBracketToken);
+                        const rightBracket = sourceCode.getLastToken(node);
+
+                        if (sourceCode.getFirstTokenBetween(leftBracket, rightBracket, { includeComments: true, filter: astUtils.isCommentToken })) {
+
+                            // Don't perform any fixes if there are comments inside the brackets.
+                            return null;
+                        }
+
+                        const tokenAfterProperty = sourceCode.getTokenAfter(rightBracket);
+                        const needsSpaceAfterProperty = tokenAfterProperty &&
+                            rightBracket.range[1] === tokenAfterProperty.range[0] &&
+                            !astUtils.canTokensBeAdjacent(String(value), tokenAfterProperty);
+
+                        const textBeforeDot = astUtils.isDecimalInteger(node.object) ? " " : "";
+                        const textAfterProperty = needsSpaceAfterProperty ? " " : "";
+
+                        return fixer.replaceTextRange(
+                            [leftBracket.range[0], rightBracket.range[1]],
+                            `${textBeforeDot}.${value}${textAfterProperty}`
+                        );
+                    }
+                });
+            }
+        }
+
+        return {
+            MemberExpression(node) {
+                if (
+                    node.computed &&
+                    node.property.type === "Literal" &&
+                    (literalTypesToCheck.has(typeof node.property.value) || astUtils.isNullLiteral(node.property))
+                ) {
+                    checkComputedProperty(node, node.property.value);
+                }
+                if (
+                    node.computed &&
+                    node.property.type === "TemplateLiteral" &&
+                    node.property.expressions.length === 0
+                ) {
+                    checkComputedProperty(node, node.property.quasis[0].value.cooked);
+                }
+                if (
+                    !allowKeywords &&
+                    !node.computed &&
+                    keywords.indexOf(String(node.property.name)) !== -1
+                ) {
+                    context.report({
+                        node: node.property,
+                        messageId: "useBrackets",
+                        data: {
+                            key: node.property.name
+                        },
+                        fix(fixer) {
+                            const dot = sourceCode.getTokenBefore(node.property);
+                            const textAfterDot = sourceCode.text.slice(dot.range[1], node.property.range[0]);
+
+                            if (textAfterDot.trim()) {
+
+                                // Don't perform any fixes if there are comments between the dot and the property name.
+                                return null;
+                            }
+
+                            if (node.object.type === "Identifier" && node.object.name === "let") {
+
+                                /*
+                                 * A statement that starts with `let[` is parsed as a destructuring variable declaration, not
+                                 * a MemberExpression.
+                                 */
+                                return null;
+                            }
+
+                            return fixer.replaceTextRange(
+                                [dot.range[0], node.property.range[1]],
+                                `[${textAfterDot}"${node.property.name}"]`
+                            );
+                        }
+                    });
+                }
+            }
+        };
+    }
+};